Sunspots Lesson. For each sunspot group, name the group and record its latitude/longitude.

Transcription

1 Sunspots Lesson Web resources: Based on the following lessons ( Solar filters ( Latitude/Longitude grid ( SOHO website ( Archived images (e.g., Activity 1: Observing the Sun Warning: Do not look directly at the Sun without a filter. Even if you can do it once, over time you will damage your eyes. Warning: NEVER look through an unfiltered telescope, period. As one of my professors told me you can actually do this twice: if you re stupid enough to do it again with the remaining eye. Galileo was the first European to discover sunspots, and he did so by looking through his unfiltered telescope. He was blind at the end of his life. Draw the Sun. For each sunspot group, name the group and record its latitude/longitude. Activity 2: Collect More Raw Data Repeat the Sun observations every day for a month. If you have limited time as we do today, use the archived images linked above. Activity 3: Analysis How long does it take for the Sun to do a full rotation (spin on its axis)? Extension: Make a graph of Latitude as a function of date (one graph for all sunspots).

2 10/20/2014 Projecting the Sun Background adapted from Society for Popular Astronomy SPA You can easily and safely observe the Sun by projecting it through a tiny hole onto a white sheet of paper. Purpose To construct a simple sun-projecting device from a telescope or binoculars Materials 1 sheet of stiff white paper telescope or binoculars (optional) tripod Procedure 1. Point a telescope or binoculars at the Sun. Do not attempt to view the Sun directly through the telescope or the binoculars! In the case of a telescope, make sure that any small finder telescope is capped, and keep the cover on one half of the binoculars. The easiest way to find the Sun is tilt your instrument to get the smallest shadow. 2. Hold a piece of white card about 15 cm behind the eyepiece to act as a screen on which you can catch the image. You should see a bright circle of light, probably blurred, on the screen. Focus the instrument until the circle is sharp. This is the disc of the Sun itself. If the eclipse is in progress you should see the Moon as a dark bite out of one edge. 3. Experiment with moving the card farther closer and further away. What effect does the distance from the card have on the image? 4. Try mounting the binoculars or telescope firmly on a tripod. The advantage of this type of projection is that several people can see the image at once. 1/2

3 10/20/2014 Projecting the Sun 2/2

4 10/20/2014 ASP: The Nearest Stars: A Guided Tour The Nearest Stars: A Guided Tour Activity: Observing the Sun Safely by John R. Percy, University of Toronto (c) 1986 Astronomical Society of the Pacific [Editor's note: Since other stars are so far away, much of the progress we are making in understanding stars in general comes from studying our own "hometown'' star, the Sun. Although most of us associate the study of astronomy with the night, in this month's activity our newsletter's newest contributing editor shows that the Sun can lend itself to useful daytime astronomy activities. (Dr. Percy is professor of astronomy at the University of Toronto in Canada and one of the world's leaders in the field of astronomy education.)] We must begin with an important warning: Never look directly at the Sun, especially when using binoculars or a telescope. Direct sunlight can cause permanent eye damage in seconds, without the victim being aware of it until it is too late. For safe direct viewing of the Sun, #14 welder's glass can be used, or a proprietary material known as Solar Skreen (Roger W. Tuthill, Inc., 11 Tanglewood Lane, Mountainside, NJ 07092). Although some telescopes are equipped with Sun filters, many of these are not reliable, and should not be used unless you are absolutely sure of what you are doing. The only reliable filters are some (but not all) which fit over the front of the telescope, and reflect away most of the light. The best way to view the Sun with binoculars or a telescope is by projection looking at an image of the Sun rather than at the Sun itself. Instructions for doing this are given below. We should note that some school officials feel that all viewing of the Sun should be forbidden. Even though there are safe ways to view the Sun, there is always a chance that some student will not take the necessary precautions, or will disobey instructions, and an accident will occur. The projection methods described below are quite safe, however and the number of astronomy-related school accidents is far less than the number encountered in other science subjects! Viewing the Sun by Projection This method is relatively safe and, with it, many people can view the Sun at once. You will need a pair of binoculars or a small telescope, a piece of plain cardboard about 30 centimeters square for the "collar,'' and a second piece of white cardboard (or paper) at least 10 centimeters square for the screen. If you use a telescope, you should mount it on a tripod. If you use binoculars, you can hold them in your hand, but it is much more convenient (and you will have a steadier image) if you improvise some sort of stand or tripod to hold them. This demonstration can be done at any time of the day when it is clear and when your class has access to direct sunlight. 1/4

5 10/20/2014 ASP: The Nearest Stars: A Guided Tour Note: Do not use binoculars whose front lenses are 50 millimeters across or wider. (Binoculars usually are described by a pair of numbers separated by an 'x', such as "7 x 3'' or "7 x 50'';; the number to the right of the 'x' is the diameter of the front lenses in millimeters.) Big lenses gather a lot of light, and the heat generated by direct sunlight in side large binoculars can damage their complex optics. Method 1. Make a cardboard collar to fit around the front end of the binocular or telescope, as shown in the figure. This shades the area where the image will be from sunlight. and (in the case of binoculars) will cover the lens which you are not using. 2. Focus the binocular or telescope on infinity by looking at a distant object (not the Sun!) in the normal way. (If you are using a telescope. use a low-magnification eyepiece.) 3. Point the binoculars or telescope at the Sun (do not look through the instrument to do this!), as shown in the figure, and adjust the direction of pointing until the image of the Sun appears on the screen. (This may take a minute or two. One useful trick is to watch the shadow of the binoculars or telescope tube: if pointed directly toward the Sun, then the sides of the tube will cast no shadows, and the instrument's shadow will be as small as it can be.) 4. Move the screen toward or away from the eyepiece until the image of the Sun fits neatly in the middle. and adjust its tilt until the Sun's image is circular. 5. Jiggle the binoculars or telescope very slightly. Any specks on the image of the Sun which do not jiggle along with the image when you do this are specks in the binoculars or telescope (or smudges on the screen), and not spots on the Sun itself. Observations When you and your students examine an image of the Sun, you will notice the following properties: 1. The image is brighter in the middle of the disc than at the edges. This effect is called limbdarkening. It occurs because, when we look at the middle of the Sun's disc, we are looking straight down into the hotter part of the Sun. At the edges of the disc, we look more obliquely, and see only the cooler, less bright gases, higher in the Sun's atmosphere. 2/4

6 10/20/2014 ASP: The Nearest Stars: A Guided Tour 2. The image moves slowly across the screen. This is due to the east-to-west motion of the Sun in the sky, caused by the rotation of the Earth. The direction of motion of the image therefore tells you which direction on the screen (and on the Sun's image) is west. 3. There may be small darks spots on the image. These are called sunspots and are regions in the outer layers of the Sun which are cooler and therefore not as bright as their surroundings. In sunspots, the Sun's magnetic field is exceptionally strong, and astronomers suspect that this is connected to their being darker than the material around them. Sunspots, when examined closely with a telescope, are seen to be very complex. They can form within a few days, and may endure and evolve for weeks or months. An Alternate Way to Project An Image of the Sun This method produces an image which is a bit fuzzy, but good enough to show large sunspots, and it is particularly suitable for observing a partial eclipse of the Sun. It is very safe, and can be used to show an image of the Sun to an entire class. You will need a small pocket mirror or hand mirror. a piece of plain cardboard to fit over the mirror (or some tape to cover it), and a piece of white cardboard or paper to use as a screen. Method 1. Cut the plain cardboard or paper so it fits over the mirror. 2. Cut or punch a very small hole, about 5 millimeters in size. in the middle of the plain cardboard. You could also use tape to cover all but a small portion of the surface of the mirror. 3. Put the mirror on a window sill in the sunlight such that it catches the rays from the Sun. Turn the room lights off and draw the window blinds so that as little as possible of the room other than the mirror is in sunlight. 4. Reflect the sunlight onto a wall of the darkened room. 5. Put the white cardboard or paper on the wall at this point, so you can use it as a screen to display the image of the Sun. Observations 1. You will notice that the image of the Sun is round (unless an eclipse is in progress), even if the hole which you cut or punched in the plain cardboard or paper was square! 2. You can also demonstrate that the size of the image of the Sun is proportional to the distance of the screen from the mirror. The larger the distance. the larger (and fainter) the image. In a more advanced class, you might want to develop an explanation for these two observations. If you do not have a classroom in which there is a sunlit window, you can do the activity outdoors. Find a place where you can catch the sunlight with your mirror, and can reflect it onto a shaded wall. (Better still, reflect it into a darkened classroom.) Again, you can use a sheet of white paper or cardboard as a screen. It takes a few minutes to discover the best arrangement for the mirror and the screen, but once you have done so, it is easy to set up the demonstration again on any following day. Further Reading About The Sun Robert Burnham: "Observing the Sun,'' Astronomy, August 1984, p. 51. B. Ralph Chou: "Safe Solar Filters,'' Sky & Telescope, August 1981, p Alan MacRobert: "Close-Up of a Star'', Sky & Telescope, May 1985, p /4

7 10/20/2014 ASP: The Nearest Stars: A Guided Tour Simon Mitton: Daytime Star (1981, Scribner's) << previous page 1 2 back to Teachers' Newsletter Main Page 4/4

8 Classroom Activities Hands-on activities for use in the classroom. Observing the Sun for Yourself observe/observe.html Classroom Activities Grade Level 3-5* Courtesy of the Stanford Solar Center PAGE ACTIVITY 12 Projecting the Sun 13 Using Remote Solar Telescopes 13 Using Your Own Telescope 14 Observing Solar Eclipses 15 Sunspot Drawings There are several ways you can observe the Sun, and hopefully sunspots, for yourself. The easiest and safest is to project the Sun by building your own pinhole camera. If you have a telescope, you will have to equip it with a solar filter or use a solar telescope that you can access via the Web. Partial solar eclipse image from Fred Espenak s Eclipse Home Page at NASA s Goddard Space Flight Center. CAUTION! Don t EVER look directly at the Sun, with or without a telescope (unless you have the proper filters). *These lessons can be adapted for higher grade levels by including telescope mirrors and observing eclipses. Teachers can also project the Sun s image through a telescope resulting in a larger image for tracking sunspots and other solar activity. 12 Living With a Star EG GSFC

9 Classroom Activities Activities courtesy of the Stanford Solar Center Projecting the Sun You can easily and safely observe the Sun by projecting it through a tiny hole onto a white sheet of paper. This simple device is called a pinhole camera. You ll need: 2 sheets of stiff white paper 1 pin A sunny day Perhaps a friend to help 1. With the pin, punch a hole in the center of one of your pieces of paper. 2. Go outside, hold the paper up and aim the hole at the Sun. (Don t look at the Sun either through the hole or in any other way! ) 3. Now, find the image of the Sun that comes through the hole. you punch two holes in the piece of paper? Try bending your paper so the images from the two holes lie on top of each other. What do you think would happen if you punched a thousand holes in your paper, and you could bend your paper so all the images lined up on top of each other? In fact, optical telescopes can be thought of as a collection of millions of pinhole images all focused together in one place! 4. Move your other piece of paper back and forth until the image rests on the paper and is in focus (i.e., has a nice, crisp edge). What you are seeing is not just a dot of light coming through the hole, but an actual image of the Sun. Experiment by making your hole larger or smaller. What happens to the image? What happens when Related Resources Bob Miller s Light Walk You can make your pinhole camera fancier by adding devices to hold up your piece of paper, or a screen to project your Sun image onto, or you can even make your pinhole camera a real camera by adding film. If you want to learn more about how light works, you can join artist Bob Miller s Web-based Light Walk at the Exploratorium. It s always an eye-opening experience for students and teachers alike. His unique discoveries will change the way you look at light, shadow, and images! Several sites give instructions for building more exotic pinhole cameras for observing the Sun: Cyberspace Middle School Jack Troeger s Sun Site Living With a Star CAUTION! Don t EVER look directly at the Sun, with or without a telescope (unless you have the proper filters). EG GSFC 13

10 Classroom Activities Activities courtesy of the Stanford Solar Center Using Remote Solar Telescopes Using Mike Rushford s robotic solar observatory in Livermore, California, you can get a real-time view of the Sun by controlling a telescope from your Web browser. At cloudy times, there are other things to do as well! Related Resources Solar Eclipse 1999 Paul Mortfield Eyes on the Skies Using Your Own Telescope The safest way to look at the Sun through your own telescope is NOT to! Looking at the Sun can cause serious damage, even blindness, to your eyes, unless you have proper filters. Galileo Galilei used telescopes to observe and track sunspots c Picture from The Galileo Project. Related Resources Viewing the Sun With a Telescope Dr. Sunspot gives more detailed information about safely viewing the Sun with a telescope and filters. Observing the Sun in H-Alpha This site gives technical information on how to observe the Sun with your own telescope using an H-alpha filter. Includes detailed information on what features of the Sun are best seen in H-alpha. By Harold Zirin, Peter V. Foukal, and David Knisely. The safest practical way to see the Sun is by eyepiece projection. Line up your telescope with the Sun, but instead of looking through the eyepiece, hold a sheet of white paper behind the eyepiece. You ll see a solar image projected onto the paper. What happens when you move the paper farther back? Experiment with the paper to get a sharp viewing contrast. You should be able to see the largest sunspots with this method. CAUTION! Don t EVER look directly at the Sun, with or without a telescope (unless you have the proper filters). 14 Living With a Star EG GSFC

11 Classroom Activities Activities courtesy of the Stanford Solar Center Observing Solar Eclipses A solar eclipse occurs when the Moon, during its monthly revolution around Earth, happens to line up exactly between Earth and the Sun. Why isn t there an eclipse every month? Because solar eclipses occur during a new moon, but not at every new moon. Most often the Moon passes a little higher or a little lower than the Sun. There is a solar eclipse about twice a year, when the Moon s and the Sun s positions line up exactly. Solar eclipse image from Fred Espenak s Eclipse Home Page at NASA s Goddard Space Flight Center. The glory of a solar eclipse comes from the dramatic view of the Sun s corona, or outer atmosphere, which we can see only when the brilliant solar disk is blocked by the Moon. The corona is not just light shining from around the disk: It is actually the outermost layer of the solar atmosphere. Although the gas is very sparse, it is extraordinarily hot (800,000 to 3,000,000 Kelvin), even hotter than the surface of the Sun! (The heating of the corona is still a mystery.) The corona shows up as pearly white streamers, their Related Resources Fred Espenak s Eclipse Home Page Eclipse: Stories From the Path of Totality shape dependent on the Sun s current magnetic fields. Thus every eclipse will be unique and glorious in its own way. A solar eclipse is only visible from a small area of Earth. It s unlikely that, during your lifetime, you will ever see a total solar eclipse directly over the place you live. Many people travel long ways to experience a total solar eclipse. If you re lucky, you might someday see a partial solar eclipse (one where the Moon doesn t quite cover all the Sun s disk) nearby. You can safely observe a TOTALLY eclipsed Sun with the naked eye, but you will need a pinhole camera, an appropriate type of welder s glass, or special Mylar glasses to safely observe the beginning and ending of a full or partial eclipse. Solar Data Anaylsis Center Eclipse Information Eclipse Paths Living With a Star CAUTION! Don t EVER look directly at the Sun, with or without a telescope (unless you have the proper filters). EG GSFC 15

12 Classroom Activities Activities courtesy of the Stanford Solar Center Sunspot Drawings Until recently, astronomers have had to rely on drawings or sketches to document what they ve seen. Charge-coupled device (CCD) cameras and other technological wonders have changed all that. Historic drawings, however, are still very important. And even today, drawings are still more accurate at recording exactly what the eye sees, unaltered by the processing of fancy electronics. Galileo Galilei (left) and sunspot drawings (above) from The Galileo Project. Related Resources Daily Sunspot Drawing Observations at Mt. Wilson Daily Sunspot Images from SOHO Galileo s Sunspot Drawings Galileo s drawings of sunspots (c. 1600) still survive today. And the solar telescope at Mt. Wilson, above Pasadena, California, has been collecting sunspot drawings since The tradition continues. You can check current sunspot drawings each day at the Websites listed here, and compare them with your own. Sunspots at the Exploratorium These classroom activities can be found at: Created by Deborah Scherrer, April Last revised by DKS on 2 December CAUTION! Don t EVER look directly at the Sun, with or without a telescope (unless you have the proper filters). 16 Living With a Star EG GSFC

13 10/20/2014 sungrid-0.gif ( ) 1/1

14 10/20/2014 solar-center.stanford.edu/solar-images/worksheet.html Sunspot Data Recording Worksheet Name: Date: Complete one of these each day of your observations For Each Sunspot Group Spot Group/ID Give each group an identifying name Latitude Longitude Comments/Changes Observed 1/1

15 10/20/2014 The Spinning Sun The Spinning Sun Does the Sun spin? Galileo Galilei, back in 1612, noticed something interesting about the Sun when he observed its sunspots. Let's see what he discovered. Data Compute Rotation Observe Rotation Your & Galileo's Discovery Other Pages Collect Your Data If you haven't already done so, collect solar data for a couple weeks by looking at images from the SOHO spacecraft. Arrange your copies or drawings of the solar disk and sunspots in order from longest-ago to the present, and flip through them slowly as if they were an animated "flip-book". Are the sunspots permanent, or do they come and go? Do they stay in the same place, or seem to move? If they move, do they move in relatively straight lines or do they wander? Galileo noticed that the spots seemed to move directly across the disk of the Sun. He thought that, if they were on the surface of the Sun, their movement might indicate that the Sun was rotating. What do you think? Compute the Sun's Rotation Rate Let's try to calculate the rotation rate of the Sun: 1/2

16 10/20/2014 The Spinning Sun By Estimating By Calculating the Spots' Angular Velocity Observe the Sun Rotate and check your answers. What Did you Discover? Would you like to compare your sunspot sketches with those made by Galileo? Galileo's drawings and animations. Did Galileo's sunspots move horizontally across the solar disk? Do your sunspots move horizontally across the solar disk? If your pictures differ from Galileo's, why do you think that is? This page is Created by Deborah Scherrer Search Home Request Spectrographs Site Map Glossary About Us Contact Us 2014 by Stanford SOLAR Center Permitted Uses Credits 2/2

17 10/20/2014 Getting Solar Images Retrieving Solar Images To discover various characteristics of the Sun, you'll need to observe it. Your "eyes" will be the SOHO spacecraft, currently circling the Sun about 1,000,000 miles from Earth. With SOHO's 12 specialized scientific instruments, we can explore everything from the Sun's glorious halo or "corona", to the violent magnetic storms on its surface, to the sound waves which help us understand the mysteries of the Sun's deep interior. Using daily pictures collected by the SOHO spacecraft, you are going to observe and record information about the currently visible sunspot groups. What do you think we can learn from watching sunspots? What You'll Need What to Do Getting the Images Examples For the Teacher Exploring Other Images What You'll Need to Get Started: Sunspot Recording Worksheet. Print out and make enough copies for each day of your observations. Latitude/longitude grids. Print these out. If you can, copy the grids onto transparency paper. An image of the Sun every day, for about 2 weeks. You will pick these up from the web (see below). Your images will look something like this, only bigger. (The sunspot groups show up as black and white blotches): 1/4

18 10/20/2014 Getting Solar Images What you are going to do: You are going to observe and track the movement of sunspots (actually, magnetically "active regions") across the Sun's visible disk. Every day, using the web, print out a copy of the internet solar image (we tell you how below). If you don't have a printer, sketch the image and sunspot groups you see. (If you have to sketch, try placing the latitude/longitude grid directly over the image on your screen to find exactly where to sketch your spots. Be careful to always have the image straight up and down.) For each of the major sunspots groups, record on your Sunspot Recording Worksheet: The name of each spot group. Make up any name you want, but make sure to keep track of which group has which name. Where (i.e. at what latitude and longitude) the spot groups lie Note whether there were any observable changes in your sunspot groups (has the group changed size, shape, disappeared altogether?) Collect images every day for days. After you've collected your data, go on to the other activities. Getting the Images: The images you will be getting are called either intensitygrams or magnetograms. They are 2/4

19 10/20/2014 Getting Solar Images retrieved every 96 minutes by the MDI instrument on the SOHO spacecraft. Before going any further, read About the Images. Don't cheat and skip this part! When you look at the image lists, use the images labeled: SOHO MDI, Magnetogram, longi. comp., Full Disk or SOHO MDI, Intensitygram, Full Disk If there is more than one magnetogram or intensitygram available, pick the one done earliest in the day (there will be a time given with each). SOHO Daily Images Help-- I Need Some Examples An example set of magnetograms (images). An example of a completed Sunspot Recording Worksheet. For the Teacher Exploring Other Images There are many interesting sites which provide solar images. The following are particularly good collections of images from various places around the Earth and in space: SOHO Synoptic Database -- Repository of recent images from other sites Space Environment Center -- A collection of images from other sites. Solar Data Analysis Center at NASA Goddard Space Flight Center in Greenbelt, 3/4

20 10/20/2014 Getting Solar Images Maryland. A collection of images from other sites. For more image sites, see our About the Sun page. Search Home Request Solar Posters Site Map Glossary About Us Contact Us 2008 by Stanford SOLAR Center Permitted Uses Credits 4/4

21 Source:( Sunspots(for(Sept,(2014( ( (

22 ( (

23 ( (

24

25 ( (

26 ( (

27 ( ( (

28 10/20/2014 Estimating the Sun's Rotation Period Estimating the Sun's Rotation Rate How can you use your sunspot data to figure out how long it takes for the Sun to spin around once? To estimate the Sun's rotation rate, let's assume that the Sun is a flat disk, just like it appears on your copies or sketches. You can use a calculator for this exercise. On your data sketches, pick a sunspot group which travels a long distance across the Sun's disk. A good choice would be a sunspot which starts out closest to the left limb (edge) of the Sun. Let's call this spot "George". You are going to figure out how long it took George to move across the Sun. 1/3

29 10/20/2014 Estimating the Sun's Rotation Period Find your picture with George closest to the left limb of the Sun. With a (metric) ruler, measure how far away from the left edge of the Sun's disk George is. Now, find the picture with George closest to the right limb of the Sun and measure it's distance. Make sure you again measure the distance starting from the left limb. 2/3

30 10/20/2014 Estimating the Sun's Rotation Period Now, measure the distance across the entire disk of the Sun (ignoring George and any of his friends). You will need to multiply this by 2 to include the back side of the Sun. Look again at your data sheets and find out what time your first sketch of George was taken. Find the time for your last sketch of George. How long did it take for George to travel from the first place to the last? (Subtract the last time from the first. In our example, it was 7 days. Now, how far around the Sun did George go? In our example, George went 6 cm (7 cm - 1 cm) and the Sun was 24 cm around. So, in this example, it took George 7 days to get 1/4 of the way around the Sun, which means that George would need 4*7 = 28 days to go all the way around (assuming he could last that long). If your numbers are more complicated than George's, then you can use your calulator to figure it out: Sun's rotation time = George's-time * (Sun's-distance / George's-distance) 28 days = 7 days * (24 cm/6 cm) If you picked a different spot or group, do you think your answer for the Sun's rotation rate would be the same? Try to find out by doing the calculation for groups at higher or lower latitudes (that is, groups that are closer or farther from the Sun's poles). You have just estimated the solar rotation rate. Your data will be more accurate if you use the Angular Velocity exercize. To see how close your estimate is and also watch an animation of the Sun spinning. Return To Sunspot Rotation Activity Search Home Request Spectrographs Site Map Glossary About Us Contact Us 2014 by Stanford SOLAR Center Permitted Uses Credits 3/3

31 10/20/2014 Calculating the Sun's Angular Velocity Calculating the Sun's Angular Velocity What is Angular Velocity? Angular velocity is how fast something travels in a circle (or on a sphere): it is the angle by which an object spins in a certain time -- its rotation rate. Imagine a clock (the old-fashioned kind with hands). The minute hand goes around the clock, a circle degrees, in 60 minutes. To find its angular velocity, or rotation rate, you need to divide the number of degrees by the number of minutes: 360 degrees / 60 minutes = 6 degrees per minute So, the minute hand's angular velocity, or rate of rotation, is 6 degrees per minute. 1/2

32 10/20/2014 Calculating the Sun's Angular Velocity How Can I Determine the Sun's Angular Velocity? We can use the movement of a sunspot to determine the Sun's rate of rotation, just like we used the minute hand of a clock. To do this accurately, you will have to use a transparent template for your sketches of the Sun's disk. The template has marked on it the degrees of longitude on a sphere. From your sketches, pick the sunspot group which is the most long-lived (that is, which appears in most of your sketches). Using your template, figure out how many degrees of Sun the spot group traveled across, and how long it took to move that far. Sun's Angular velocity = degrees the spot has covered / time it took for the spot to travel Sun's rotation rate = 360 degrees / angular velocity Going Further If the Sun has been particularly active and you have sunspots sketched at different latitutes on the Sun's surface, compute the angular velocity for different sunspot groups which appear at varying latitudes. Do you get the same solar rotation rate for each set? If not, why not? Want more information on the Sun's rotation? Return To Sunspot Rotation Activity Search Home Request Spectrographs Site Map Glossary About Us Contact Us 2014 by Stanford SOLAR Center Permitted Uses Credits 2/2